Glycerol plasticised chitosan: a study of biodegradation via carbon dioxide evolution and nuclear magnetic resonance

The biodegradation of neat chitosan, glycerol plasticised chitosan films and their corresponding clay-based nano-biocomposites has been studied in simulated aerobic soil and composting environments using a respirometric method. The rate of biodegradation was much faster in soil and all test samples achieved close to 100% biodegradation within 70 days. During biodegradation under aerobic composting conditions the neat chitosan samples achieved approx 65% biodegradation and the plasticised chitosan samples achieved >85% biodegradation within 180 days. Additionally, nano-clay additives had no significant effect on the overall biodegradability of the chitosan-based materials during composting. High-resolution solid-state NMR studies were performed to examine the chemical structures of the plasticized chitosan and their nano-biocomposites. NMR studies indicated that the glycerol plasticizer was extracted into wet compost within first few days while acetic acid remained through strong hydrogen bonding with chitosan during the degradation process.